DESCRIPTION

The getgrnam() function returns a pointer to a structure containing the
broken-out fields of the record in the group database (e.g., the local
group file /etc/group, NIS, and LDAP) that matches the group name name.
The getgrgid() function returns a pointer to a structure containing the
broken-out fields of the record in the group database that matches the
group ID gid.
The group structure is defined in <grp.h> as follows:
struct group {
char *gr_name; /* group name */
char *gr_passwd; /* group password */
gid_t gr_gid; /* group ID */
char **gr_mem; /* group members */
};
For more information about the fields of this structure, see group(5).
The getgrnam_r() and getgrgid_r() functions obtain the same information
as getgrnam() and getgrgid(), but store the retrieved group structure
in the space pointed to by grp. The string fields pointed to by the
members of the group structure are stored in the buffer buf of size
buflen. A pointer to the result (in case of success) or NULL (in case
no entry was found or an error occurred) is stored in *result.
The maximum needed size for buf can be found using sysconf(3) with the
argument _SC_GETGR_R_SIZE_MAX.

RETURNVALUE

The getgrnam() and getgrgid() functions return a pointer to a group
structure, or NULL if the matching entry is not found or an error
occurs. If an error occurs, errno is set appropriately. If one wants
to check errno after the call, it should be set to zero before the
call.
The return value may point to a static area, and may be overwritten by
subsequent calls to getgrent(3), getgrgid(), or getgrnam(). (Do not
pass the returned pointer to free(3).)
On success, getgrnam_r() and getgrgid_r() return zero, and set *result
to grp. If no matching group record was found, these functions return
0 and store NULL in *result. In case of error, an error number is
returned, and NULL is stored in *result.

ERRORS

0 or ENOENT or ESRCH or EBADF or EPERM or ...
The given name or gid was not found.
EINTR A signal was caught.
EIO I/O error.
EMFILE The maximum number (OPEN_MAX) of files was open already in the
calling process.
ENFILE The maximum number of files was open already in the system.
ENOMEM Insufficient memory to allocate group structure.
ERANGE Insufficient buffer space supplied.

FILES

CONFORMINGTO

SVr4, 4.3BSD, POSIX.1-2001.

NOTES

The formulation given above under "RETURN VALUE" is from POSIX.1-2001.
It does not call "not found" an error, hence does not specify what
value errno might have in this situation. But that makes it impossible
to recognize errors. One might argue that according to POSIX errno
should be left unchanged if an entry is not found. Experiments on
various UNIX-like systems shows that lots of different values occur in
this situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and
probably others.

SEEALSO

COLOPHON

This page is part of release 3.35 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://man7.org/linux/man-pages/.
2010-10-21 GETGRNAM(3)